Imperial College London

Professor Camille Petit

Faculty of EngineeringDepartment of Chemical Engineering

Professor of Materials Engineering
 
 
 
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Contact

 

+44 (0)20 7594 3182camille.petit Website

 
 
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Location

 

522ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

128 results found

Schukraft GEM, Moss B, Kafizas AG, Petit Cet al., 2022, Effect of Band Bending in Photoactive MOF-Based Heterojunctions., ACS Appl Mater Interfaces

Semiconductor/metal-organic framework (MOF) heterojunctions have demonstrated promising performance for the photoconversion of CO2 into value-added chemicals. To further improve performance, we must understand better the factors which govern charge transfer across the heterojunction interface. However, the effects of interfacial electric fields, which can drive or hinder electron flow, are not commonly investigated in MOF-based heterojunctions. In this study, we highlight the importance of interfacial band bending using two carbon nitride/MOF heterojunctions with either Co-ZIF-L or Ti-MIL-125-NH2. Direct measurement of the electronic structures using X-ray photoelectron spectroscopy (XPS), work function, valence band, and band gap measurements led to the construction of a simple band model at the heterojunction interface. This model, based on the heterojunction components and band bending, enabled us to rationalize the photocatalytic enhancements and losses observed in MOF-based heterojunctions. Using the insight gained from a promising band bending diagram, we developed a Type II carbon nitride/MOF heterojunction with a 2-fold enhanced CO2 photoreduction activity compared to the physical mixture.

Journal article

Hwang J, Azzan H, Pini R, Petit Cet al., 2022, H2, N2, CO2, and CH4 unary adsorption isotherm measurements at low and high pressures on zeolitic imidazolate framework ZIF-8, Journal of Chemical & Engineering Data, ISSN: 0021-9568

Excess adsorption of CO2, CH4, N2, and H2 on ZIF-8 was measured gravimetrically in the pressure range ranging from vacuum to 30 MPa at 298.15, 313.15, 333.15, 353.15, and 394.15 K using a magnetic suspension balance. The textural properties of the adsorbent material─i.e., skeletal density, surface area, pore volume, and pore-size distribution─were estimated by helium gravimetry and N2 (77 K) physisorption. The adsorption isotherms were fitted with the Sips isotherm model and the virial equation, and the values of isosteric heat of adsorption and Henry constants for the gases were determined using the latter.

Journal article

Petit C, L'Hermitte A, Dawson D, Ferrer P, Roy K, Held G, Tian T, Ashbrook Set al., 2021, Formation mechanism and porosity development in porous boron nitride, The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, Vol: 125, Pages: 27429-27439, ISSN: 1932-7447

Porous boron nitride (BN) has proven promising as a novel class of inorganic materials in the field of separations and particularly adsorption. Owing to its high surface area and thermal stability, porous BN has been researched for CO2 capture and water cleaning, for instance. However, research remains at the laboratory scale due to a lack of understanding of the formation mechanism of porous BN, which is largely a “black box” and prevents scale up. Partial reaction pathways have been unveiled, but they omit critical steps in the formation, including the porosity development, which is key to adsorption. To unlock the potential of porous BN at a larger scale, we have investigated its formation from the perspective of both chemical formation and porosity development. We have characterized reaction intermediates obtained at different temperatures with a range of analytical and spectroscopic tools. Using these analyses, we propose a mechanism highlighting the key stages of BN formation, including intermediates and gaseous species formed in the process. We identified the crucial formation of nonporous carbon nitride to form porous BN with release of porogens, such as CO2. This work paves the way for the use of porous BN at an industrial level for gas and liquid separations.

Journal article

Rajagopalan AK, Petit C, 2021, Material Screening for Gas Sensing Using an Electronic Nose: Gas Sorption Thermodynamic and Kinetic Considerations, ACS SENSORS, Vol: 6, Pages: 3808-3821, ISSN: 2379-3694

Journal article

Butler EL, Reid B, Luckham PF, Guldin S, Livingston AG, Petit Cet al., 2021, Interparticle Forces of a Native and Encapsulated Metal-Organic Framework and Their Effects on Colloidal Dispersion, ACS APPLIED MATERIALS & INTERFACES, Vol: 13, Pages: 45898-45906, ISSN: 1944-8244

Journal article

Taddei M, Petit C, 2021, Engineering metal-organic frameworks for adsorption-based gas separations: from process to atomic scale, Molecular Systems Design & Engineering, Vol: 6, Pages: 841-875, ISSN: 2058-9689

Metal-organic frameworks (MOFs) are the object of intense research targeting their deployment as adsorbents for a wide range of gas separations, such as CO2 capture, biogas upgrading, air separation and small hydrocarbons separation. The scope of this review is to provide chemists, material scientists and engineers with an overview of the state-of-the-art and of the main challenges in the field of adsorption-based gas separations using MOFs. To do so, we first discuss current gas separation challenges for which adsorption could play a role. The following three sections of the paper describe process-level considerations in the design, selection and deployment of MOFs as sorbents and subsequently focus on material-level considerations. Both the process and the material aspects cover experimental and computational work. Going from the process scale to the atomic scale, we aim to highlight the links and synergies between the two and identify the current barriers that hamper the development of adsorption-based gas separations using MOFs as sorbents. Throughout the article, we also provide fundamental and technical information related to MOFs design, synthesis, characterisation and sorption testing.

Journal article

Xiong Y, Woodward RT, Danaci D, Evans A, Tian T, Azzan H, Ardakani M, Petit Cet al., 2021, Understanding trade-offs in adsorption capacity, selectivity and kinetics for propylene/propane separation using composites of activated carbon and hypercrosslinked polymer, CHEMICAL ENGINEERING JOURNAL, Vol: 426, ISSN: 1385-8947

Journal article

Rampal N, Ajenifuja A, Tao A, Balzer C, Cummings MS, Evans A, Bueno-Perez R, Law DJ, Bolton LW, Petit C, Siperstein F, Attfield MP, Jobson M, Moghadam PZ, Fairen-Jimenez Det al., 2021, The development of a comprehensive toolbox based on multi-level, high-throughput screening of MOFs for CO/N-2 separations, CHEMICAL SCIENCE, Vol: 12, Pages: 12068-12081, ISSN: 2041-6520

Journal article

Danaci D, Bui M, Petit C, Mac Dowell Net al., 2021, En route to zerio emissions for power and industry with amine-based post-combustion capture, Environmental Science and Technology (Washington), Vol: 55, Pages: 10619-10632, ISSN: 0013-936X

As more countries commit to a net-zero GHG emission target, we need a whole energy and industrial system approach to decarbonization rather than focus on individual emitters. This paper presents a techno-economic analysis of monoethanolamine-based post-combustion capture to explore opportunities over a diverse range of power and industrial applications. The following ranges were investigated: feed gas flow rate between 1–1000 kg ·s–1, gas CO2 concentrations of 2–42%mol, capture rates of 70–99%, and interest rates of 2–20%. The economies of scale are evident when the flue gas flow rate is <20 kg ·s–1 and gas concentration is below 20%mol CO2. In most cases, increasing the capture rate from 90 to 95% has a negligible impact on capture cost, thereby reducing CO2 emissions at virtually no additional cost. The majority of the investigated space has an operating cost fraction above 50%. In these instances, reducing the cost of capital (i.e., interest rate) has a minor impact on the capture cost. Instead, it would be more beneficial to reduce steam requirements. We also provide a surrogate model which can evaluate capture cost from inputs of the gas flow rate, CO2 composition, capture rate, interest rate, steam cost, and electricity cost.

Journal article

Tian T, Hou J, Ansari H, Xiong Y, L'Hermitte A, Danaci D, Pini R, Petit Cet al., 2021, Mechanically stable structured porous boron nitride with high volumetric adsorption capacity, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 13366-13373, ISSN: 2050-7488

Journal article

Schukraft GEM, Woodward RT, Kumar S, Sachs M, Eslava S, Petit Cet al., 2021, Hypercrosslinked polymers as a photocatalytic platform for visible-light-driven CO2 photoreduction using H2O, ChemSusChem: chemistry and sustainability, energy and materials, Vol: 14, Pages: 1720-1727, ISSN: 1864-5631

The design of robust, high‐performance photocatalysts is key for the success of solar fuel production by CO2 conversion. In this study, hypercrosslinked polymer (HCP) photocatalysts have been developed for the selective reduction of CO2 to CO, combining excellent CO2 sorption capacities, good general stabilities, and low production costs. HCPs are active photocatalysts in the visible light range, significantly outperforming the benchmark material, TiO2 P25, using only sacrificial H2O. It is hypothesized that superior H2O adsorption capacities facilitate access to photoactive sites, improving photocatalytic conversion rates when compared to sacrificial H2. These polymers are an intriguing set of organic photocatalysts, displaying no long‐range order or extended π‐conjugation. The as‐synthesized networks are the sole photocatalytic component, requiring no added cocatalyst doping or photosensitizer, representing a highly versatile and exciting platform for solar‐energy conversion.

Journal article

Stafford J, Uzo N, Farooq U, Favero S, Wang S, Chen H-H, L'Hermitte A, Petit C, Matar Oet al., 2021, Real-time monitoring and hydrodynamic scaling of shear exfoliated graphene, 2D Materials, Vol: 8, Pages: 1-17, ISSN: 2053-1583

Shear-assisted liquid exfoliation is a primary candidate for producing defect-free two-dimensional (2D) materials. A range of approaches that delaminate nanosheets from layered precursors in solution have emerged in recent years. Diverse hydrodynamic conditions exist across these methods, and combined with low-throughput, high-cost characterization techniques, strongly contribute to the wide variability in performance and material quality. Nanosheet concentration and production rate are usually correlated against operating parameters unique to each production method, making it difficult to compare, optimize and predict scale-up performance. Here, we reveal the shear exfoliation mechanism from precursor to 2D material and extract the derived hydrodynamic parameters and scaling relationship that are key to nanomaterial output and common to all shear exfoliation processes. Our investigations use conditions created from two different hydrodynamic instabilities—Taylor vortices and interfacial waves—and combine materials characterization, fluid dynamics experiments and numerical simulations. Using graphene as the prototypical 2D material, we find that scaling of concentration of few-layer nanosheets depends on local strain rate distribution, relationship to the critical exfoliation criterion, and precursor residence time. We report a transmission-reflectance method to measure concentration profiles in real-time, using low-cost optoelectronics and without the need to remove the layered precursor material from the dispersion. We show that our high-throughput, in situ approach has broad uses by controlling the number of atomic layers on-the-fly, rapidly optimizing green solvent design to maximize yield, and viewing live production rates. Combining the findings on the hydrodynamics of exfoliation with this monitoring technique, we unlock targeted process intensification, quality control, batch traceability and individually customizable 2D materials on-demand.

Journal article

Danaci D, Webley PA, Petit C, 2021, Guidelines for techno-economic analysis of adsorption processes, Frontiers in Chemical Engineering, Vol: 2, ISSN: 2673-2718

Techno-economic analyses (TEAs) of CO2 capture technologies have risen in popularity, due to growing interest in meeting CO2 emissions reduction targets. Adsorption processes are one of the technologies proposed for CO2 capture, and although difficult, standardisation of TEAs for adsorption should be attempted. The reason is that TEAs are often referred to as input data to other forms of modelling, to guide policy, and act as summaries for those unfamiliar with adsorption processes. Herein, we discuss the aspects that should be considered when conducting TEAs for CO2 adsorption processes, we present the implications of choices made at the TEA stage and offer guidance on best practice. Overall, our aim is to make TEAs of adsorption processes more widely accessible to the adsorption community, and also more generally to communities engaged in the evaluation of CCS technologies.

Journal article

Farooq U, Stafford J, Petit C, Matar OKet al., 2020, Numerical simulations of a falling film on the inner surface of a rotating cylinder, Physical Review E, Vol: 102, Pages: 043106 – 1-043106 – 13, ISSN: 2470-0045

A flow in which a thin film falls due to gravity on the inner surface of a vertical, rotating cylinder is investigated. This is performed using two-dimensional (2D) and 3D direct numerical simulations, with a volume-of-fluid approach to treat the interface. The problem is parameterized by the Reynolds, Froude, Weber, and Ekman numbers. The variation of the Ekman number (Ek), defined to be proportional to the rotational speed of the cylinder, has a strong effect on the flow characteristics. Simulations are conducted over a wide range of Ek values (0≤Ek≤484) in order to provide detailed insight into how this parameter influences the flow. Our results indicate that increasing Ek, which leads to a rise in the magnitude of centrifugal forces, produces a stabilizing effect, suppressing wave formation. Key flow features, such as the transition from a 2D to a more complex 3D wave regime, are influenced significantly by this stabilization and are investigated in detail. Furthermore, the imposed rotation results in distinct flow characteristics such as the development of angled waves, which arise due to the combination of gravitationally and centrifugally driven motion in the axial and azimuthal directions, respectively. We also use a weighted residuals integral boundary layer method to determine a boundary in the space of Reynolds and Ekman numbers that represents a threshold beyond which waves have recirculation regions.

Journal article

Ye Z, Schukraft GEM, L'Hermitte A, Xiong Y, Brillas E, Petit C, Sires Iet al., 2020, Mechanism and stability of an Fe-based 2D MOF during the photoelectro-Fenton treatment of organic micropollutants under UVA and visible light irradiation, WATER RESEARCH, Vol: 184, ISSN: 0043-1354

Journal article

Butler EL, Petit C, Livingston AG, 2020, Poly(piperazine trimesamide) thin film nanocomposite membrane formation based on MIL-101: Filler aggregation and interfacial polymerization dynamics, JOURNAL OF MEMBRANE SCIENCE, Vol: 596, ISSN: 0376-7388

Journal article

Evans A, Cummings M, Decarolis D, Gianolio D, Shahid S, Attfield M, Law G, Petit Cet al., 2020, Optimisation of Cu+ impregnation of MOF-74 to improve CO/N2 and CO/CO2 separations, RSC Advances: an international journal to further the chemical sciences, Vol: 10, Pages: 5152-5162, ISSN: 2046-2069

Carbon monoxide (CO) purification from syngas impurities is a highly energy and cost intensive process. Adsorption separation using metal–organic frameworks (MOFs) is being explored as an alternative technology for CO/nitrogen (N2) and CO/carbon dioxide (CO2) separation. Currently, MOFs' uptake and selectivity levels do not justify displacement of the current commercially available technologies. Herein, we have impregnated a leading MOF candidate for CO purification, i.e. M-MOF-74 (M = Co or Ni), with Cu+ sites. Cu+ allows strong π-complexation from the 3d electrons with CO, potentially enhancing the separation performance. We have optimised the Cu loading procedure and confirmed the presence of the Cu+ sites using X-ray absorption fine structure analysis (XAFS). In situ XAFS and diffuse reflectance infrared Fourier Transform spectroscopy analyses have demonstrated Cu+–CO binding. The dynamic breakthrough measurements showed an improvement in CO/N2 and CO/CO2 separations upon Cu impregnation. This is because Cu sites do not block the MOF metal sites but rather increase the number of sites available for interactions with CO, and decrease the surface area/porosity available for adsorption of the lighter component.

Journal article

Danaci D, Bui M, Mac Dowell N, Petit Cet al., 2020, Exploring the limits of adsorption-based CO2 capture using MOFs with PVSA – from molecular design to process economics, Molecular Systems Design and Engineering, Vol: 5, Pages: 212-231, ISSN: 2058-9689

Metal-organic frameworks (MOFs) have taken the materials science world by storm, with potentials of near infinite possibilities and the panacea for adsorption-based carbon capture. Yet, no pilot-scale (or larger-scale) study exists on MOFs for carbon capture. Beyond material scalability issues, this clear gap between the scientific and engineering literature relates to the absence of suitable and accessible assessment of MOFs in an adsorption process. Here, we have developed a simple adsorbent screening tool with process economics to evaluate adsorbents for post-combustion capture, while also considering factors relevant to industry. Specifically, we have assessed the 25 adsorbents (22 MOFs, 2 zeolites, 1 activated carbon) against performance constraints – i.e. CO2 purity and recovery – and cost. We have considered four different CO2 capture scenarios to represent a range of CO2 inlet concentrations. The cost is compared to that of amine-based solvents for which a corresponding model was developed. Using the model developed, we have conceptually assessed the materials properties and process parameters influencing the purity, recovery and cost in order to design the ‘best’ adsorbent. We have also set-up a tool for readers to screen their own adsorbent. In this contribution, we show that minimal N2 adsorption and moderate enthalpies of adsorption are key in obtaining good process performance and reducing cost. This stands in contrast to the popular approaches of maximizing CO2 capacity or surface area. Of the 22 MOFs evaluated, UTSA-16 shows the best performance and lowest cost for post-combustion capture, having performance in-line with the benchmark, zeolite 13X. Mg-MOF-74 performs poorly. The cost of using the adsorbents remains overall higher than that of an amine-based absorption process. Ultimately, this study provides specific directions for material scientists to design adsorbents and assess their performance at the process scale. This

Journal article

Thompson JF, Bellerjeau C, Marinick G, Osio-Norgaard J, Evans A, Carry P, Street RA, Petit C, Whiting GLet al., 2019, Intrinsic Thermal Desorption in a 3D Printed Multifunctional Composite CO2 Sorbent with Embedded Heating Capability, ACS APPLIED MATERIALS & INTERFACES, Vol: 11, Pages: 43337-43343, ISSN: 1944-8244

Journal article

Shankar R, Sachs M, Francas L, Lubert-Perquel D, Kerherve G, Regoutz A, Petit Cet al., 2019, Porous boron nitride for combined CO2 capture and photoreduction, Journal of Materials Chemistry A, Vol: 7, Pages: 23931-23940, ISSN: 2050-7488

Porous and amorphous materials are typically not employed for photocatalytic purposes, like CO2 photoreduction, as their high number of defects can lead to low charge mobility and favour bulk electron–hole recombination. Yet, with a disordered nature can come porosity, which in turn promotes catalyst/reactant interactions and fast charge transfer to reactants. Here, we demonstrate that moving from h-BN, a well-known crystalline insulator, to amorphous BN, we create a semiconductor, which is able to photoreduce CO2 in the gas/solid phase, under both UV-vis and pure visible light and ambient conditions, without the need for cocatalysts. The material selectively produces CO and maintains its photocatalytic stability over several catalytic cycles. The performance of this un-optimized material is on par with that of TiO2, the benchmark in the field. For the first time, we map out experimentally the band edges of porous BN on the absolute energy scale vs. vacuum to provide fundamental insight into the reaction mechanism. Owing to the chemical and structural tunability of porous BN, these findings highlight the potential of porous BN-based structures for photocatalysis particularly solar fuel production.

Journal article

Evans AD, Cummings MS, Luebke R, Brown MS, Favero S, Attfield MP, Siperstein F, Fairen-Jimenez D, Hellgardt K, Purves R, Law D, Petit Cet al., 2019, Screening metal–organic frameworks for dynamic CO/N2 separation using complementary adsorption measurement techniques, Industrial & Engineering Chemistry Research, Vol: 58, Pages: 18336-18344, ISSN: 0888-5885

Carbon monoxide (CO)/nitrogen (N2) separation is a particularly challenging separation, yet it is the one with great industrial relevance for its use in petrochemical synthesis. Although an expensive cryogenic step can be used to perform such separation, it remains ineffective in purifying CO from syngas streams with a significant N2 content. Taking advantage of the lower energy requirement of adsorption processes, we have explored the use of metal–organic frameworks (MOFs) as adsorbents for this difficult separation. We have screened a range of MOF candidates for CO/N2 separation covering a range of chemical and textural features, using the flux response technology to evaluate their dynamic performance for throughput testing alongside equilibrium uptake measurements. We have identified Ni-MOF-74 and Co-MOF-74 as the most promising candidates because of their high metal density and strong metal–CO interactions. We have investigated further the effect of N2 impurity concentrations upon CO/N2 separation using breakthrough adsorption testing and cyclic testing (up to 20 cycles). Overall, using multiple adsorption measurement techniques, this study demonstrates the CO/N2 dynamic separation performance of M-MOF-74 and its ability to be applied for an industrially relevant separation.

Journal article

Schukraft G, Petit C, 2019, Green synthesis and engineering applications of metal-organic frameworks, Sustainable Nanoscale Engineering: From Materials Design to Chemical Processing, Pages: 139-162, ISBN: 9780128146811

Book chapter

Taddei M, Schukraft GM, Warwick MEA, Tiana D, McPherson MJ, Jones DR, Petit Cet al., 2019, Band gap modulation in zirconium-based metal–organic frameworks by defect engineering, Journal of Materials Chemistry A, Vol: 7, Pages: 23781-23786, ISSN: 2050-7488

<p>A simple defect engineering approach to systematically tune the band gap of the prototypical zirconium-based metal–organic framework UiO-66 is reported. Defect engineered materials display enhanced photocatalytic activity.</p>

Journal article

Zhao D, Thallapally PK, Petit C, Gascon Jet al., 2019, Advanced Porous Materials: Design, Synthesis, and Applications in Sustainability, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 7, Pages: 7997-7998, ISSN: 2168-0485

Journal article

Marchesini S, Wang X, Petit C, 2019, Porous boron nitride materials: Influence of structure, chemistry and stability on the adsorption of organics, Frontiers in Chemistry, Vol: 7, ISSN: 2296-2646

Porous boron nitride (BN) is structurally analogous to activated carbon. This materialis gaining increasing attention for its potential in a range of adsorption and chemicalseparation applications, with a number of recent proof-of-concept studies on the removalof organics from water. Today though, the properties of porous BN—i.e., surface area,pore network, chemistry—that dictate adsorption of specific organics remain vastlyunknown. Yet, they will need to be optimized to realize the full potential of the materialin the envisioned applications. Here, a selection of porous BN materials with varied porestructures and chemistries were studied for the adsorption of different organic molecules,either directly, through vapor sorption analyses or as part of a water/organic mixture in theliquid phase. These separations are relevant to the industrial and environmental sectorsand are envisioned to take advantage of the hydrophobic character of the BN sheets.The materials were tested and regenerated and their physical and chemical featureswere characterized before and after testing. This study allowed identifying the adsorptionmechanisms, assessing the performance of porous BN compared to benchmarks in thefield and outlining ways to improve the adsorption performance further.

Journal article

Crake A, Christoforidis K, Gregg A, Moss B, Kafizas A, Petit Cet al., 2019, The effect of materials architecture in TiO2/MOF composites on CO2 photoreduction and charge transfer, Small, Vol: 15, Pages: 1-12, ISSN: 1613-6810

CO2 photoreduction to C1/C1+ energized molecules is a key reaction of solar fuel technologies. Building heterojunctions can enhance photocatalysts performance, by facilitating charge transfer between two heterojunction phases. The material parameters that control this charge transfer remain unclear. Here, it is hypothesized that governing factors for CO2 photoreduction in gas phase are: i) a large porosity to accumulate CO2 molecules close to catalytic sites and ii) a high number of “points of contact” between the heterojunction components to enhance charge transfer. The former requirement can be met by using porous materials; the latter requirement by controlling the morphology of the heterojunction components. Hence, composites of titanium oxide or titanate and metal–organic framework (MOF), a highly porous material, are built. TiO2 or titanate nanofibers are synthesized and MOF particles are grown on the fibers. All composites produce CO under UV–vis light, using H2 as reducing agent. They are more active than their component materials, e.g., ≈9 times more active than titanate. The controlled composites morphology is confirmed and transient absorption spectroscopy highlights charge transfer between the composite components. It is demonstrated that electrons transfer from TiO2 into the MOF, and holes from the MOF into TiO2, as the MOF induces band bending in TiO2.

Journal article

Crake A, Christoforidis K, Godin R, Moss B, Kafizas A, Zafeiratos S, Durrant J, Petit Cet al., 2019, Titanium dioxide/carbon nitride nanosheet nanocomposites for gas phase CO2 photoreduction under UV-visible irradiation, Applied Catalysis B: Environmental, Vol: 242, Pages: 369-378, ISSN: 0926-3373

In the field of photocatalysis and particularly that of CO2 photoreduction, the formulation of nanocomposites provids avenues to design a material platform with a unique set of structural, optoelectronic and chemical features thereby addressing shortcomings of single-phase materials and allowing synergistic effects. In this work, inorganic/organic composite photocatalysts for CO2 reduction comprised of titanium dioxide (TiO2) and carbon nitride nanosheets (CNNS) were synthesized using a hydrothermal in-situ growth method. Specifically, pre-formed CNNS were used to synthesize TiO2/CNNS heterostructures with control over the TiO2 facet formation. This synthesis approach improved the catalytic properties by increasing CO2 adsorption capacity and facilitating charge transfer. The materials were characterised by various spectroscopic, imaging, and analytical techniques to investigate their structural (from nano- to macroscale), chemical, and optical properties. TiO2 nanoparticles were efficiently grown on the CNNS. The CO2 adsorption capacity of the composites was measured, and they were tested for CO2 photoreduction under UV-Vis illumination with hydrogen as the reducing agent in a heterogeneous gas-solid system to combine CO2 capture and conversion into a single-step process. Catalytic tests were performed without adding any precious metal co-catalyst. The composites exhibited enhanced CO2 adsorption capacity and photocatalytic CO2 conversion compared to their constituent materials (> ten-fold increase) and outperformed the TiO2 P25 benchmark material. The TiO2/CNNS composite with more {001} TiO2 facets was the most catalytically active. Further investigations using transient absorption spectroscopy (TAS) revealed the control of facet formation improved interfacial transfer at the TiO2/CNNS junction. A photocatalytic mechanism was proposed based on the spectroscopic analyses as well as the CO2 adsorption, and CO2 conversion results.

Journal article

Shankar R, Marchesini S, Petit C, 2019, Enhanced hydrolytic stability of porous boron nitride via the control of crystallinity, porosity, and chemical composition, Journal of Physical Chemistry C, Vol: 123, Pages: 4282-4290, ISSN: 1932-7447

Porous boron nitride is gaining significant attention for applications in molecular separations, photocatalysis, and drug delivery. All these areas call for a high degree of stability (or controlled stability) over a range of chemical environments, particularly under humid conditions. The hydrolytic stability of the various forms of boron nitride, including porous boron nitride, has been sparingly addressed in the literature. Here, we map the physical–chemical properties of the material to its hydrolytic stability for a range of conditions. Using analytical, imaging, and spectroscopic techniques, we identify the links between the hydrolytic instability of porous boron nitride and its limited crystallinity, high porosity, as well as the presence of oxygen atoms. To address this instability issue, we demonstrate that subjecting the material to a thermal treatment leads to the formation of crystalline domains of h-BN exhibiting a hydrophobic character. The heat-treated sample displays an enhanced hydrolytic stability, while maintaining a high porosity. This work provides an effective and simple approach to producing stable porous boron nitride structures and will progress the implementation of the material in applications involving interfacial phenomena.

Journal article

Danaci D, Bui M, Dowell NM, Petit Cet al., 2019, An adsorbent screening tool with process economics for carbon capture by PVSA

Conference paper

Dias E, Christoforidis K, Francas L, Petit Cet al., 2018, Tuning thermally treated graphitic carbon nitride for H₂ evolution and CO₂ photoreduction: The effects of material properties and mid-gap states, ACS Applied Energy Materials, Vol: 1, Pages: 6524-6534, ISSN: 2574-0962

Graphitic carbon nitride (g-C3N4) is regarded as an attractive photocatalyst for solar fuel production, i.e., H2 evolution and CO2 photoreduction. Yet, its structural, chemical and optoelectronic properties are very much dependent on the synthesis method and are likely to contribute differently whether H2 evolution or CO2 reduction is considered. Little is known about this aspect making it difficult to tailor g-C3N4 structure and chemistry for a specific photoreaction. Herein, we create g-C3N4 of varying chemical, structural and optical features by applying specific thermal treatments and investigating the effects of the materials properties on solar fuel production. The samples were characterized across scales using spectroscopic, analytical and imaging tools, with particular attention given to the analyses of trap states. In the case of H2 evolution, the reaction is controlled by light absorption and charge separation enabled by the presence of trap states created by N vacancies. In the case of CO2 photoreduction, reactant adsorption appears as a dominating factor. The analyses also suggest that the thermal treatment leads to the formation of trap states located close to the valence band of g-C3N4.

Journal article

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